1. Field of the Invention
The present invention relates to an apparatus and method for transmitting/receiving a Physical Uplink Shared CHannel (PUSCH) signal in a cellular radio communication system supporting a Carrier Aggregation (CA) scheme. More particularly, the present invention relates to an apparatus and method for transmitting/receiving a PUSCH signal if an UpLink (UL) Configuration for carrier aggregated cells is different from a DownLink (DL) Configuration for the carrier aggregated cells in a Time Division Duplexing (TDD) communication system supporting a CA scheme.
2. Description of the Related Art
Long Term Evolution (LTE) technology supports two duplexing modes, i.e., Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD).
FIG. 1 is a schematic diagram of a frame structure of LTE TDD system according to the related art.
Referring to FIG. 1, a length of each radio frame is 10 milliseconds (ms). Each radio frame is equally divided into two half-frames and the length of each half-frame is 5 ms. Each half-frame includes eight time slots of 0.5 ms and three special domains. The total length of the three special domains is 1 ms. The three special domains respectively are a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP) and an Uplink Pilot Time Slot (UpPTS), and each sub-frame consists of two consecutive time slots.
Transmissions in the TDD system include a transmission from a base station to a User Equipment (UE) (referred to as downlink) and a transmission from the UE to the base station (referred to as uplink). Based on the frame structure shown in FIG. 1, the uplink and downlink share 10 sub-frames within each 10 ms, and each sub-frame is either configured for the uplink or configured for the downlink. The sub-frame configured for the uplink is referred to as an uplink sub-frame, while the sub-frame configured for the downlink is referred to as a downlink sub-frame. TDD system supports seven Uplink/Downlink Configurations, as shown in Table 1, D represents a downlink sub-frame, U represents an uplink sub-frame, S represents a special sub-frame including the above three special domains.
TABLE 1ConfigurationBreakingSub-frame indexserial numberpoint cycle01234567890 5 msDSUUUDSUUU1 5 msDSUUDDSUUD2 5 msDSUDDDSUDD310 msDSUUUDDDDD410 msDSUUDDDDDD510 msDSUDDDDDDD610 msDSUUUDSUUD
LTE TDD system supports a Hybrid Automatic Repeat reQuest (HARQ) mechanism, the basic principles of which include that a base station allocates uplink resources for a UE, the UE transmits uplink data to the base station using the uplink resources, the base station receives the uplink data and sends HARQ indication information to the UE, and the UE retransmits the uplink data in accordance with the indication information. Specifically, the UE carries the uplink data via a Physical Uplink Shared CHannel (PUSCH), the base station carries scheduling and control information of the PUSCH, i.e., the UL Grant, via a Physical Downlink Control CHannel (PDCCH), and the base station carries the HARQ indication information via a Physical HARQ Indicator CHannel (PHICH). In the above process, a timing position of the PUSCH in one transmission and the subsequent retransmission timing positions are determined based on pre-configured timing relationships, which include a timing relationship from the UL Grant to the PUSCH, a timing relationship from the PHICH to the PUSCH, and a timing relationship from the PUSCH to the PHICH. The above three timing relationships are hereinafter referred to as the PUSCH timing relationship.
Firstly, the timing relationship from the UL Grant or PHICH to the PUSCH in the LTE and LTE-Advanced (LTE-A) is introduced.
For the timing relationship from the UL Grant to the PUSCH, it is assumed that a UE receives UL Grant in a downlink sub-frame n (n is an index number of the sub-frame, and the following is the same), the UL Grant is used for controlling the PUSCH within the uplink sub-frame n+k. Values of k are defined in Table 2. Specifically, for TDD Uplink/Downlink Configurations (or referred to as Uplink/Downlink Configuration for short) 1 to 6, the number of the uplink sub-frames is less than or equal to the number of the downlink sub-frames (S frame can be used as a downlink sub-frame), and for a certain downlink sub-frame n, a unique PUSCH timing relationship may be configured by a unique value of k, which is reflected in Table 2. Here, the PUSCH may not be scheduled within a downlink sub-frame, or the PUSCH within one uplink sub-frame may only be scheduled. For the TDD Uplink/Downlink Configuration 0, the number of the uplink sub-frames is greater than the number of the downlink sub-frames, and the PDCCH of each downlink sub-frame needs to be schedule the PUSCHs within two uplink sub-frames, so that the value of k could not be unique. The Uplink index (UL index) technology is needed to support the scheduling of the PUSCHs within two uplink sub-frames in the PDCCH, wherein different k values are used for indexing different PUSCHs. For example, when the UE receives the PDCCH within a downlink sub-frame 0, the PDCCH schedules the PUSCHs within an uplink sub-frame 4 and/or an uplink sub-frame 7. When the UE receives the PDCCH within a downlink sub-frame 1, the PDCCH schedules the PUSCHs within an uplink sub-frame 7 and/or an uplink sub-frame 8. Table 2 showing a timing relationship from the UL Grant to the PUSCH is provided below.
TABLE 2Configuration Downlink sub-frame index nserial number012345678904, 76, 74, 76, 716464244344444454677775
For the timing relationship from the PHICH to the PUSCH, in LTE and LTE-A, a PHICH resources block is independently assigned for the PUSCH within each uplink sub-frame. It is assumed that the UE receives the PHICH within a downlink sub-frame n, and the PHICH is used for controlling the PUSCH within an uplink sub-frame n+j. Values of j are defined in Table 3. Specifically, for TDD Uplink/Downlink Configurations 1 to 6, the number of the uplink sub-frames is less than or equal to the number of the downlink sub-frames, and for a certain downlink sub-frame n, a unique PUSCH timing relationship may be configured by a unique value of j, which is reflected in Table 3. Here, the PHICH resources block may not be configured within a downlink sub-frame, or the PHICH resources block of only one uplink sub-frame may be configured, For the TDD Uplink/Downlink Configuration 0, the number of the uplink sub-frames is greater than the number of the downlink sub-frames, so that the value of j could not be unique, wherein two PHICH resources blocks are configured within a downlink sub-frame 0 and a downlink sub-frame 5, i.e., PHICH resources block 0 and PHICH resources block 1, different j values are used for different PHICH resources. For example, when the UE receives the PHICH within a downlink sub-frame 0, the PUSCH within the uplink sub-frame 4 and/or uplink sub-frame 7 may be triggered. Table 3 showing a timing relationship from the PHICH to the PUSCH is provided below.
TABLE 3Configuration Downlink sub-frame index nserial number012345678904, 774, 7716464244344444454677775
Secondly, the timing relationship from the PUSCH to the PHICH in the LTE and LTE-A is introduced.
For TDD Uplink/Downlink Configurations 1 to 6, when the UE receives the PHICH within a downlink sub-frame n, the PHICH indicates HARQ-ACK information of the PUSCH within an uplink sub-frame n-h. Values of h are shown in Table 4.
For TDD Uplink/Downlink Configuration 0, as two PHICH resources blocks are configured, when the UE receives the PHICH at the PHICH resources block 0 within the downlink sub-frame n, the PHICH may control the PUSCH within the uplink sub-frame n-h in accordance with the definition of h in Table 4. When the UE receives the PHICH at the PHICH resources block 1 within the downlink sub-frame 0 or the downlink sub-frame 5, the PHICH controls the PUSCH transmission within the uplink sub-frame n-6. Table 4 showing a timing relationship from the PUSCH to the PHICH is provided below
TABLE 4Uplink/Downlink Downlink sub-frame index nConfiguration01234567890747414646266366646656664746
According to Table 2, Table 3 and Table 4 of the timing relationship, a PUSCH timing relationship may be determined when a Cell adopts a particular TDD Uplink/Downlink Configuration, so that the PUSCH transmission may be achieved according to the PUSCH timing relationship.
However, with the requirements of users on data transfer rate becoming higher and higher, LTE-A technology is also proposed. In LTE-A, a greater bandwidth is capable through a combination of a plurality of Component Carriers (CC), and this technique is referred to as Carrier Aggregation (CA). For example, a 100 MHz bandwidth may be obtained through the combination of five 20 MHz CCs. Here, each CC is referred to as a Cell. The base station may configure a UE to work in more than one Cell, in which a Cell is known as the Primary Cell (PCell), and other Cells are known as the Secondary Cell (SCell).
For the TDD system using CA, through making the plurality of Cells in one combination using the same Uplink/Downlink Configuration, the PUSCH timing relationship configured for one Cell in LTE may be fully reused.
In addition, two scheduling policies are also defined in LTE-A, the first policy is cross-carrier scheduling, and the second policy is non-cross-carrier scheduling. The cross-carrier scheduling indicates that a Physical Downlink Shared CHannel (PDSCH) data transmission in one Cell is scheduled by the PDCCH sent by another Cell. The non-cross-carrier scheduling indicates that the PDSCH data transmission in one Cell is scheduled by the PDCCH sent by the Cell itself.
While for the condition that the TDD Uplink/Downlink Configurations of the Carrier Aggregated Cells are exactly the same, the cross-carrier scheduling may fully reuse the PUSCH timing relationship in the non-cross-carrier scheduling, as described below with reference to FIG. 2.
FIG. 2 is a schematic diagram illustrating the cross-carrier scheduling and the non-cross-carrier scheduling according to the related art.
Referring to FIG. 2, Cell 1 and Cell 2 all adopt TDD Uplink/Downlink Configuration 1. For the non-cross-carrier scheduling, in Cell 2, the UE receives PUSCH data of Cell 2 scheduled by the UL Grant. For the cross-carrier scheduling, in Cell 1, the UE receives the PUSCH data of Cell 2 scheduled by the UL Grant.
It can be seen that, in the TDD system using CA, under the circumstance that the TDD Uplink/Downlink Configurations of the Carrier Aggregated Cells are exactly the same, either in the cross-carrier scheduling or in the non-cross-carrier scheduling, the PUSCH timing relationship may reuse the PUSCH timing relationship in the above-mentioned TDD system which does not adopt CA, without modifying the protocol.
In LTE, there is an advantage of reducing adjacent channel interference when Uplink/Downlink Configurations of the Carrier Aggregated Cells are not exactly the same. Thus, an important topic for LTE-A is how to achieve the PUSCH transmission under the circumstance that the TDD Uplink/Downlink Configurations of the Carrier Aggregated Cells are different.
Obviously, for the circumstance that the Uplink/Downlink Configurations of Carrier Aggregated Cells are not exactly the same, the PUSCH timing relationship could not be simply fully-reused; thus there is a need for a solution on this issue.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.